WO2002087366A2 - Filter tow made from crimped endless cellulose acetate filaments - Google Patents

Abstract

The invention relates to a filter tow made from crimped endless cellulose acetate filaments, whereby the filaments form at least two connected fibre bundles with the same filament titre of at least 600 filaments. The filament titres differ from bundle to bundle by at least 1 dtex. Furthermore a filter tow is disclosed with a crimp ratio of more than 40 %, said filaments comprising at least 22 crimp turns per filament length.

Description

 Filter Tow

The invention relates to a filter tow for the production of cigarette filters with a comparatively low filtration capacity, the draw resistance retention characteristic of which has been chosen such that their use in filling flavor cigarettes with a degree of ventilation of more than 25% with an acceptable draw resistance of the cigarette and filter insert weight is possible.

The majority of the cigarette filters used today are made from filter tow, which consists of endless cellulose-2.5-acetate filaments. These filters are called acetate filters. The cigarettes, which are manufactured and sold in the European Union, can be divided into the following classes according to the condensate values in the smoke: - Filling - Flavor

- medium

- Light and

- Ultra light cigarettes

All these cigarettes are ventilated due to the maximum quantity regulation (90/239 / EEC) regarding the condensate values. The degree of ventilation depends on the one hand on the target value of condensate and on the other hand on the filtration performance of the filter used. The following table provides an overview of the currently common values:

The majority of products currently on sale have a diameter of 7.8 + 0.2 mm with a cigarette length of 85 - 120 mm. There are also niches - products that differ significantly in their design features from the best-selling products. To meet this diversity of product requirements To be right, the filter tow industry provides a multitude of different ones

Types of tea that can essentially be described by the following features:

Filament titer (dtex) 1.6 - 8.8; Total titer (dtex) 17,000 - 60,000; Crimp index (%) 25 max. 38; Number of crimped sheets per cm: 10 max. 20;

The following description of the object of the invention is based solely on the

Class of filling flavor products. A typical filter cigarette of the class

Filling Flavor has the following typical characteristics, all of which are only indicative. They only serve as a basis for the calculation of further explanations.

lengths:

- Cigarette: 84 mm

- Filter: 21 mm

- Tobacco strand: 63 mm

- Tipping: 26 mm

Diameter:

- Filter: 7.80 mm

- Cigarette: 7.85 mm

draw resistance:

- filter: 66 mm \

- tobacco rod: 50 mm \

- Cigarette: 100 mm.

• Filter Tow Specification: 3.0 Y 35 (filament titer: 3.33 dtex; total titer: 38,900, cross-sectional shape of the filaments: Y)

• Tobacco blend: American blend

• ventilation:

Degree of ventilation: 20%

Position ventilation zone: 11 mm

Smoke values:

- condensate: 12 mg

- Nicotine: 0.9 mg

- Carbon monoxide (CO): 14 mg

retentions:

- condensate: 42%

- nicotine: 38%

- Carbon monoxide (CO): none

Due to a new maximum quantity regulation (2000 / C 150E / 03) of the European Union, the filling flavor products in particular will have to change drastically in their design features, since from 1.1.04 not only the condensate value, but also the nicotine - and especially the CO - Value will be regulated with regard to its maximum value. The challenge when converting the product according to the new EU regulation is that the change in the products must be designed in such a way that the maximum permitted quantities are optimally matched Smoke taste can be hit on the 10mg condensate, 1mg nicotine and 10 mg CO per cigarette. In other words: A future 1: 1 ratio of CO / tar should be aimed for the filling flavor products. As can be seen from the table above, this ratio is 1.17 in this example.

Based on model calculations that only take into account a change in the filter ventilation, it can be assumed that a filter ventilation of approx. 35% is required to reduce CO from today's, in the above calculation example 14 mg to 10 mg per cigarette in the future. An increase in the degree of ventilation in an otherwise unchanged product inevitably leads to a reduction in the cigarette pull resistance.

For the consumer, however, an optimal smoky taste means that the draw resistance of the cigarette must not drop significantly below the current value of approx. 100 mmWS. The result of increasing the degree of ventilation is that if the other filter parameters, such as draft resistance, diameter, position of the ventilation zone and filter length, are retained, the draft resistance of the cigarette is significantly reduced. The resulting cigarette draw resistance can be calculated using the following equation, which is based on a laminar flow model:

P _v = P ₀ - V x (P ₀ - P _F x L _v / L _F ) mean:

Py: draft resistance of the ventilated cigarette (mm WS)

P ₀ : _draw resistance of unventilated cigarette: = draw resistance [filter + tobacco rod] (mmWS) P _F : filter _draw resistance (mmWS) V: degree of ventilation filter (%) / 100

Ly: distance of the ventilation zone from the mouth side (mm) L _F : filter length (mm)

The open draw resistance for the specified sample cigarette with a degree of ventilation of 35% is therefore only 88 mm WS (instead of originally 100 mmWS). Such a drop in cigarette resistance is clearly perceptible to the smoker and must therefore be maintained by a

Raising the filter pull resistance (in the example above, to approx. 80 mm water column) can be compensated. This increase in the filter pull resistance inevitably leads to an increase in the CO / tar ratio, since only the tar, but not the CO values are influenced by the filter pull resistance (increasing the pull resistance leads to a reduction in the tar values).

The draft resistance retention ratios must therefore be redefined for future products in the "Filling Flavor" category. The filter used to manufacture the filter must be used to set a 1: 1 CO / tar ratio and to ensure an acceptable product regarding draft resistance of the cigarette Tow can be tailored to these requirements. In this context, the following requirements can be defined:

1. The filter tow must be suitable to be able to manufacture filters with the current (but preferably still higher) tensile resistances. 2. To achieve the 1: 1 CO / tar ratio, the filtration performance of the filters produced from the filter tow according to the invention must be significantly lower than the retentions common today, given the tensile resistance of the filter. 3. The additional material consumption resulting from an increase in the filament titer must be kept within limits. For a given filter diameter and length, the retention of a filter depends exclusively on the tensile resistance and the filament titer. An increase in the filament titer and a reduction in the tensile resistance, for example, lead to a decrease in the filtration performance (and vice versa). Since the relationships are very complex in nature, filter calculation programs are used today to estimate the extent of such changes. The calculation program is an example here

Cable ^® (Capability Line Expert; Copyright of Rhodia Acetow GmbH 1998, Freiburg,

Germany) from Rhodia Acetow.

According to the prior art, the retention of a filter is therefore reduced by raising the filament titer. Model calculations suggest that in the future the fila ment titer must be increased by at least 0.5-1.5 dtex in order to meet the requirements for filtration performance. However, the filter tow specifications currently on the market (the mean total titer of all specifications is approx. 35 ktex) are not suitable for covering the required tensile resistance range with the required minimum foot titer (retention) (Cable ^® calculation program from Rhodia Acetow GmbH). According to the state of the art, this problem can only be solved with a monoaceatate filter by simultaneously drastically raising the total titer to well over 45,000 dtex.

Such solutions, such as a filter tow of the type 4.5 Y 55 (see Fig. 2) according to the prior art, would then meet the tensile resistance and retention requirements, but would increase consumption compared to today's products Filter tow of> 35%.

In the previous version, the statements were limited to the group of filling flavor cigarettes. However, if a CO / tar ratio of 1: 1 is generally aimed for, then the explanations regarding the expansion of the tensile resistance ranges apply to all filament titers. That means: The task specified below generally covers the filament titer spectrum of 1.6 - 8.8 dtex that is common today.

The object of the invention is therefore to provide a filter tow with which it is possible to produce filters with a CO / tar ratio of the filtration performance of 1: 1.

To meet the above requirements, two fundamentally independent approaches are proposed according to the invention, the characteristics of which can be combined if necessary.

The first solution according to the invention relates to a filter tow made of crimped, endless cellulose acetate filaments, the filaments forming at least two coherent fiber bundles of the same filament titer of at least 600 filaments, which differ in their filament titer from fiber bundle to fiber bundle by at least 1 dtex. This solution gives particularly excellent results in terms of filtration performance, since it has surprisingly been found that a filter which consists of a such inhomogeneously distributed blended tow has a significantly lower tar retention than a product made from a conventional tow with a uniform filament titer distribution or a blended tow with a homogeneous filament distribution (see Figure 3).

The second solution is implemented by a filter tow, which has a more intense and at the same time significantly finer crimp structure than the products common today. A filter tow with a crimp index of more than 40% is specified in claim 4, the filaments having at least 22 crimp arcs per cm of filament length. This filter tow particularly meets the highest requirements with regard to the filter draw resistance. The values achieved will be exceeded if the crimp index is more than 42%, the filaments preferably having more than 25 crimped sheets per cm.

In order to obtain an optimal filtration performance of the filters at the same time, a filter tow with a filament titer of more than 3.33 dtex and a total titer which is less than 44,000 dtex, preferably less than 40,000 dtex, is proposed. Limiting the total titer leads to an acceptable additional consumption of filter tow.

The design and the advantages of the two solutions according to the invention are described as follows:

The crimp index I _x is a measure of the intensity of the crimp. The ripple index of a filter tow is determined by a tensile test (relationship force / elongation). It is defined as the ratio of the stretched length L ₂ under test load minus the initial length to the initial length under preload Li:

The test load is 25 N and the preload is 2.5 N. The clamping length is 250 mm. The crimp index is determined in a tensile test with a constant stretching speed of 300 mm / min on a G02 device from Borgwaldt GmbH, Hamburg. Per 10 individual measurements are recorded. The test is carried out under a standard climate: 20 ° C and 60% relative humidity (the measurement method for the crimp index is described in the Cable program under the "Help" button).

The ripple index values of today's filter tow specifications are usually between 25 and 35%. Rhodia Acetow is the only manufacturer worldwide to offer specifications under the name SK, in a filament titer range of <2.78 dtex, which cover a crimp index range of more than 35% - maximum 38%.

As already mentioned, the crimp index is a measure of the intensity of the crimp and thus the position of the characteristic. In this context, a characteristic curve is understood to mean the performance range of a filter tow, which specifies the tensile resistance range in which a filter tow can be processed under a given diameter and filter rod length under customary processing conditions. The characteristic curve for this work area describes the relationship between tensile resistance and weight. The relationship between the position of the characteristic curve and the crimp index is shown using the example of a filter tow of the type 2.1 Y 35 HK (filament titer: 2.33 dtex; total titer: 38,900; cross-sectional shape of the filaments: Y; crimp index: 32%) and a 2.1 Y 35 SK (Filament titre: 2.33dtex; total titre: 38.900, cross-sectional shape of the filaments: Y; crimp index: 36%) shown in Fig. 1.

The above object is achieved in that a filter tow is produced which has a crimp index of more than 40%, preferably more than 42%. This index is mandatory in order to cover the corresponding range of train resistance. The crimp index is influenced on the one hand by the frequency and on the other hand by the amplitude of the crimp arcs. The number of crimps is a measure of the fineness of the crimp. Typical values today are 10 to max. 20 crimped sheets per cm of filament length. The SK-Tows cited above usually have 15-18 curling sheets per cm.

Surprisingly, it was found that such an index can only be achieved with an acceptable tear strength of the filter tow if the crimp is made hyper-fine. The filter tow according to the invention therefore has an index of more than 40% for the filaments on average more than 22, preferably more than 25,

Crimped sheets per cm of filament length. Such a filter tow can be processed on conventional filter rod machines into cigarette filters which are at a comparable level of tensile resistance as filters which were produced from the specifications which are common today. Figure 2 shows the working range of a tow of the type 4.5 Y 35 according to the invention (filament titer 5.0 dtex; total titer: 38,900 dtex) in comparison to a conventional filter tow of type 3.0 Y 35 (filament titer 3.33 dtex; total titer: 38,900 dtex) , or a conventional 4.5 Y 55 and a conventional 4.5 Y 35.

From Figure 2 it is clear that compared to today's situation (3.0 Y 35) in the solution according to the invention (example 1: 4.5 Y 35), due to the increase in the filament titer, significantly more material is consumed, this additional consumption but compared to a traditional solution according to the state of the art (4.5 Y 55) is significantly lower.

For the gentle expression of a hyperfine crimp, certain general conditions in the manufacturing process must be observed. Before the crimping process, the filter tow band contains the following components that soften the acetate filaments: water, acetone, and avivage components. It is known that these softening components have a lasting effect on the curling process. For example, US 5,225,277 describes the effect of acetone and belt temperatures on the stability of the crimp. The method described there can be used to produce products with up to 19.7 crimped sheets per cm. No information is given in this document about the crimp index. From the data given there (tensile resistance, tow specification and machine settings), however, the aforementioned cable program can be used to estimate a crimp index which is definitely below 35%.

JP OS 56 - 53223 describes the effects of steam treatment of the belt before entering the crimping machine. Products with 16 crimps per cm are described. There is no information about the crimp index. It has now surprisingly been found that a hyperfine crimp can be produced effectively and without too drastic filament damage if the sum of the soft components at the time of the crimping process the value of 25 weight

% exceeds. It is irrelevant in which concentrations the individual components are present. The sum of the individual components is determined experimentally gravimetrically by drying a sample at 150 ° C (20 min), which is drawn directly after the crimping machine.

As already mentioned, one of the solutions to the problem according to the invention relates to a filter tow with a so-called mixed titer.

DE 29 16 062 describes such a filter tow and the cigarette filters produced therefrom. In contrast to the filter tow according to the invention, the filaments are distributed as uniformly as possible there (see column 2, lines 22ff in DE 29 16 062). In the version according to DE 29 16 062, this has the effect that the material used for the filters to be manufactured decreases with the same tensile resistance, but the retentions of the filters increase significantly as a result of the even distribution of the filaments.

The aim of the invention described here is also to save material, but at the same time the retention of the filter made from the filter tow should be significantly smaller than that which is achieved when corresponding filters are made from a filter tow with a uniform filament titer. This is achieved if it is ensured in the product according to the invention that the filaments form coherent fiber bundles of the same filament titer of at least 600 filaments, preferably more than 1000 filaments, which in their filament titer from fiber bundle to fiber bundle form by at least 1 dtex, preferably by more than Distinguish 1.5 dtex. The filter tow contains at least two, preferably more than five areas of filament bundles of the same filament titer. The advantage of this embodiment is that the filament bundles of the same filament titer agglomerate in the filter and thus form areas of low or high tensile resistance. A filter made from such a mixed titer tow accordingly has similar properties with regard to tensile resistance and retention as are described, for example, in JP2000000085 for a classic core-shell filter. There are no restrictions regarding the crimp index and the number of crimp sheets per cm for this filter tow. In a preferred embodiment of the invention, however, a product is produced with a crimp index of more than 33%, preferably greater than 35%.

The advantages of the invention according to claims 8 to 10 can be summarized as follows: Because of the combination of features according to the invention, working areas are accessible with respect to tensile resistance which are not available today. This makes it possible to raise the filament titer to the extent that a significantly lower filtration performance of the products can be achieved by applying the teaching according to claim 10 with a given resistance. Due to the mentioned restriction regarding the total titer, the material consumption during filter production can be limited.

However, a combination of the embodiments according to at least one of claims 1 to 7 with one or more of claims 8 to 10 is particularly advantageous. This embodiment allows a further significant reduction in the total titer to be used and thus leads to further savings potential with regard to material consumption.

The invention is explained in more detail below on the basis of exemplary embodiments.

Comparative example (tow of the 4.5 Y 55 type): A spinning solution with a concentration of 30 percent by weight cellulose acetate in acetone is prepared, filtered and then pressed through nozzles. The water content of the spinning solution is 1.5%. The number of holes, size and number of holes in the spinnerets is selected so that a 4.5 Y 55 tow is ultimately produced. The leveling dosage is set so that an oil layer of 0.5%) results. The tape is crimped with a conventional stuffer box crimping machine in such a way that a filter tow with a crimp index of 30.5%) is obtained after drying and packaging. The sum of the softening components is 22.3%. The tensile strength of the tow is determined to be 143 N. The number of crimped sheets is 15.8 / cm filament length.

The product is processed on a conventional filter rod machine KDF2 / AF2 from Hauni, Hamburg, to filter rods with a length of 126 mm and a diameter of 7.8 mm. The formation of fluff during processing of the product is due and, extrapolated to the consumption of one ton of material, is 0.5g / ton. The characteristic curve of the product, shown in Figure 2, covers a resistance range of 310 - 460 mmWS.

Example 1:

A spinning solution with a concentration of 30 percent by weight cellulose acetate in acetone is prepared, filtered and then pressed through nozzles. The water content of the spinning solution is 3%. The number of holes, size and number of holes in the spinnerets are selected so that a filter tow of the 4.5 Y 35 type is ultimately produced. The finish dosage is adjusted so that an oil overlay of 1.3% results. The resulting tape is crimped with a conventional stuffer box crimping machine in such a way that a filter tow with a crimp index of 43.5% is produced after drying and packaging. The sum of the softening components is 29%. The tear strength of the tow is determined with I H N. The number of crimps is 26 / cm filament length.

The product is processed on a conventional filter rod machine KDF2 / AF2 from Hauni to filter rods with a length of 126 mm and a diameter of 7.8 mm. The lint formation during the processing of the product is inconspicuous and, calculated on the consumption of one ton of material, is 2.8 g / ton. The characteristic curve of the product, shown in Figure 2, covers a resistance range of 298 - 505 mm WS.

Example 2:

A spinning solution with a concentration of 30 percent by weight cellulose acetate in acetone is prepared, filtered and then pressed through nozzles. The water content of the spinning solution is 3%. The number of holes, size and number of holes in the spinnerets is selected so that a 4.5 Y 32 is ultimately produced on average. In contrast to the previous examples, the spinning machine is divided into six zones, zone by zone alternating a high (1185 filaments 6.9 den = 7.65 dtex per zone) and a low filament denier (1185 filaments 2.1 den = 2.3 dtex per zone) is spun. The avivage dosage is set so that an oil result of 1.3%. The resulting tape is crimped with a conventional stuffer box crimping machine in such a way that a filter tow with a crimp index of 39.8% is produced after drying and packaging. The sum of the softening components is 27.5%. The tensile strength of the tow is determined to be 129 N. The number of crimped sheets is 23.1 / cm filament length.

The product is processed on a standard filter rod machine KDF2 / AF2 from Hauni to filter rods with a length of 126 mm and a diameter of 7.8 mm. The lint formation during the processing of the product is inconspicuous and, extrapolated to the consumption of one ton of material, amounts to 0.9 g / ton.

The characteristic curve of the product covers a tension resistance range of 267 - 487 mmWS.

*. *

Claims

claims 1. Filter tow made of crimped, endless cellulose acetate filaments, characterized in that the filaments form at least two continuous fiber bundles of the same filament titer of at least 600 filaments, which differ in their filament titer from fiber bundle to fiber bundle by at least 1 dtex. 2. Filter Tow according to claim 1, characterized in that the filaments form more than five continuous fiber bundles of the same filament titer. 3. Filter Tow according to claim 1 or 2, characterized in that the individual fiber bundles contain more than 1000 filaments. 4. Filter Tow according to one of claims 1 to 3, characterized in that the filament titre of the filaments differ from fiber bundle to fiber bundle by more than 1.5 dtex. 5. Filter Tow according to one of claims 1 to 4, characterized in that the Crimp index is more than 33% and the number of crimp sheets per cm is greater than 15. 6. Filter Tow according to one of claims 1 to 5, characterized in that the crimp index is more than 35%. 7. Filter Tow according to one of the preceding claims, characterized in that the crimp index is more than 40%, preferably more than 42%, and the number of crimped sheets per cm exceeds 22. 8. Filter tow made of crimped, endless cellulose acetate filaments, characterized in that the filter tow has a crimp index of more than 40% and the filaments have at least 22 crimped sheets per cm of filament length. 9. Filter Tow according to claim 8, characterized in that the crimp index is more than 42% and the filaments have more than 25 crimp sheets per cm. 10. Filter Tow according to claim 8 or 9, characterized in that the filament titer is greater than 3.3 dtex and the total titer is less than 44,000 dtex, preferably less than 40,000 dtex. * * *